Revision indicia, such as revision bars (or change bars), are commonly placed next to text that has changed since the last time that text was published. In structured publishing systems, revision bar insertion is typically triggered by the presence of semantic markup. Classically, this revision markup is either entered by an author or programmatically inserted by a text-differencing program. During the process of turning structured content, such as XML (Extensible Markup Language), into formatted output (a process known as rendering), the structured publishing system uses the revision markup to control where revision bars are placed in the formatted output.
A variety of publishing systems for presenting information products are known. Such publishing systems may rely upon a repository of information that may be stored in a standardized format, such as XML or SGML (Standard Generalized Markup Language). Examples of existing XML-based publishing systems include those products available from Arbortext, Inc. of Ann Arbor, Mich., and from XY Enterprise, Inc. of Reading, Mass.
Although desirable results have been achieved using such conventional publishing systems, there is room for improvement. For example, there is currently no efficient way of maintaining revision information for multiple information products derived from the same XML source if those information products have different revision cycles.